Comparison of vaccines prepared from leptospires grown in a serum medium and in a chemically defined medium.

Two types of leptospiral vaccines consisting of the organisms of four strains (strain Shibaura of Icterohaemorrhagiae serogroup, strain Akiyami A of serotype autumnalis, strain Akiyami B of serotype hebdomadis and strain Akiyami C of serotype australis) were prepared; one type was prepared from these strains grown in KORTHOF'S medium containing normal rabbit serum (the serum medium vaccine), and the other was made from mutants grown in SHENBERG'S chemically defined medium (the chemically defined medium vaccine). The protein nitrogen was lower and electron microscopical impurities were fewer in the chemically defined medium vaccine than in the serum medium vaccine. The rabbit serum was detected by the precipitation test in the serum medium vaccine. The results of the potency test did not differ between the two vaccines. The decrease in body weight of animals one day after intraperitoneal injection was induced equally by both vaccines. These results indicate that the chemically defined medium vaccine is preferable to the serum medium vaccine.